There are 46,000 different glaciers in the world’s highest-peaking mountain range, and they span three million hectares. Scientists are pretty sure that they’re melting. But it’s hard to say exactly which ones, or how fast, because only 600 are being monitored by researchers. Of those, 95% are shrinking. And a high-profile effort to synthesize available data on the Himalaya’s glaciers led to one of the most famous miscalculations in the recent history of climate science.Scientists on the Intergovernmental Panel on Climate Change included this incendiary finding in its 2007 report: “Glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate. Its total area will likely shrink from the present 500,000 to 100,000 km by the year 2035.”
If that was the case, the Himalayas would be disappearing faster than any other frozen place on the planet. That’s a spectacular, holy shit kind of scenario that makes for some solidly apocalyptic imagery—glaciers on the world’s largest mountain range, gone in 25 years! The water supply for hundreds of millions—gone! The glaciers on the most famous mountains we’ve got—gone! Crazy.It was. The data the researchers relied on wasn’t peer-reviewed, and it turned out that the IPCC had included some inaccurate information and botched the prediction. The climate skeptics went wild, and scientists issued an embarrassing retraction. Remember, climate science isn’t like other fields—there’s far less room for error, as no other field except maybe evolutionary biology has a determined cohort of skeptics seeking to exploit its every shortcoming. Climate scientists are scrutinized, ridiculed, and constantly battered, especially in the right-wing corners of the media. It’s not fair, but when your findings threaten to disrupt the decades-long dominance of an enormously wealthy industry like fossil fuels, that’s the end result.Even though science is predicated on making mistakes and correcting them, vested interests and screaming skeptics make sure each error is broadcast especially loudly—they seek to make each mistake a referendum on the validity of the field itself.
So, in a quest for a different set of data, researchers turned to GRACE. The Gravity Recovery and Climate Experiment, a joint mission of NASA and the German Aerospace Center, was launched in 2002. A pair of twin satellites make detailed measurements of earth’s gravity field, from which scientists can draw conclusions about mass—a useful tool for calculating things like glacier loss in mountainous regions largely unreachable by foot.As the science journal Nature notes, a “2010 study using measurements taken by the [GRACE] satellite reported that glaciers in the Himalayas and the Tibetan plateau were shedding roughly 50 gigatonnes of ice a year.” But once again, they weren’t. Just two years later, another batch of scientists re-interpreted the data, and found that “ice loss was only one tenth of that amount.” A single dataset, two radically different results. Perhaps we need a third go round to break the tie. So here’s the newest study on Himalayan ice melt:Now a third study of Himalayan glaciers, using a different satellite called ICESat, indicates that these glaciers lost an average of 12 gigatonnes ice a year between 2003 and 20083 … The new estimate raises further questions about satellite and field measurements of alpine glaciers, and "will set the cat among the pigeons," says Graham Cogley, a remote-sensing expert … Although the ICESat results show twice as much ice loss as the re-interpreted GRACE data, this figure is still three times lower than regional losses estimated on the basis of field studies.
This satellite measures the glaciers’ surface elevations with a laser altimeter. And indeed, the new study shows the Himalaya glaciers shrinking 21 centimeters a year, which is way less than the melt we’re seeing at the ice caps. As a result, there’s still no definitive read on just how quickly the Himalayan glaciers are disappearing, even with NASA’s most sophisticated satellites out gathering data. Lonnie Thompson, the famed glaciologist, says we’ve got to correct that, and pronto. He told Nature that “there is an urgent need to understand why these satellite studies differ from each other and from some field measurements, what their sources of errors are, and how they can be better calibrated.”More better satellites, please. Of course, the indisputable through-line is that the glaciers are indeed retracting, and that a warming climate is almost certainly the culprit. But it would be nice to know whether we’re looking at a couple of decades or a couple centuries before one of the world’s most populous regions runs out of its primary water supply.
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